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931.
In this paper, we study the decay property of the solutions to the Bernoulli–Euler-type equation with a local degenerate dissipation. 相似文献
932.
Cho DW Latham JA Park HJ Yoon UC Langan P Dunaway-Mariano D Mariano PS 《The Journal of organic chemistry》2011,76(8):2840-2852
New types of tetrameric lignin model compounds, which contain the common β-O-4 and β-1 structural subunits found in natural lignins, have been prepared and carbon-carbon bond fragmentation reactions of their cation radicals, formed by photochemical (9,10-dicyanoanthracene) and enzymatic (lignin peroxidase) SET-promoted methods, have been explored. The results show that cation radical intermediates generated from the tetrameric model compounds undergo highly regioselective C-C bond cleavage in their β-1 subunits. The outcomes of these processes suggest that, independent of positive charge and odd-electron distributions, cation radicals of lignins formed by SET to excited states of sensitizers or heme-iron centers in enzymes degrade selectively through bond cleavage reactions in β-1 vs β-O-4 moieties. In addition, the findings made in the enzymatic studies demonstrate that the sterically large tetrameric lignin model compounds undergo lignin peroxidase-catalyzed cleavage via a mechanism involving preliminary formation of an enzyme-substrate complex. 相似文献
933.
We compared efficiencies of different PMD compensation feedback methods against transmission signal bandwidth,including NRZ, RZ, CRZ format under various duty cycles. We found that the critical factor determining the efficiency of PMD compensation is not the modulation format, but the spectral bandwidth of the transmission signal. 相似文献
934.
Mark E. Ridgeway Jeremy J. Wolff Joshua A. Silveira Cheng Lin Catherine E. Costello Melvin A. Park 《International Journal for Ion Mobility Spectrometry》2016,19(2-3):77-85
Analysis of molecules by ion mobility spectrometry coupled with mass spectrometry (IMS-MS) provides chemical information on the three dimensional structure and mass of the molecules. The coupling of ion mobility to trapping mass spectrometers has historically been challenging due to the large differences in analysis time between the two devices. In this paper we present a modification of the trapped ion mobility (TIMS) analysis scheme termed “Gated TIMS” that allows efficient coupling to a Fourier Transform Ion Cyclotron Resonance (FT-ICR) analyzer. Analyses of standard compounds and the influence of source conditions on the TIMS distributions produced by ion mobility spectra of labile ubiquitin protein ions are presented. Ion mobility resolving powers up to 100 are observed. Measured collisional cross sections of ubiquitin ions are in excellent qualitative and quantitative agreement to previous measurements. Gated TIMS FT-ICR produces results comparable to those acquired using TIMS/time-of-flight MS instrument platforms as well as numerous drift tube IMS-MS studies published in the literature. 相似文献
935.
Isaacs L Park SK Liu S Ko YH Selvapalam N Kim Y Kim H Zavalij PY Kim GH Lee HS Kim K 《Journal of the American Chemical Society》2005,127(51):18000-18001
We report the isolation, characterization, and recognition behavior of iCB[6] and iCB[7], which are diastereomers of CB[6] and CB[7], respectively, containing a single inverted glycoluril unit. Product resubmission experiments establish that these inverted CB[n] are intermediates in the mechanism of CB[n] formation. As a consequence of the inverted glycoluril ring, these inverted cucurbiturils possess a permanent dipole moment, are slightly smaller than their diastereomers, show distinctive selectivity in their recognition behavior, and report directly on the contents of their hydrophobic cavity. 相似文献
936.
Da Yeon Park 《Tetrahedron letters》2007,48(9):1633-1636
Poly-substituted nitrobenzenes were synthesized from Baylis-Hillman adducts via the [3+3] annulation strategy as the key step. 1,3-Dinitroalkanes served as the 1,3-dinucleophilic component and the Baylis-Hillman acetates as a 1,3-dielectrophilic part. 相似文献
937.
Co/Rh (Co:Rh = 2:2) heterobimetallic nanoparticles derived from Co(2)Rh(2)(CO)(12) react with alkynes and alpha,beta-unsaturated aldehydes such as acrolein, crotonaldehyde, and cinnamic aldehyde and release products resulting from [2 + 2 + 1]cycloaddition of alkyne, carbon monoxide, and alkene. alpha,beta-Unsaturated aldehydes act as a CO and alkene source. These reactions produce 2-substituted cyclopentenones. 相似文献
938.
Sung-Seen Choi Boyoung Chu Seung Goo Lee Sung Wook Lee Sung Soon Im Seong Hun Kim Jong Kyoo Park 《Journal of Sol-Gel Science and Technology》2004,30(3):215-221
Titania-doped silica fibers were prepared by electrospinning of the sol of silica containing titania. The electrospun fibers had ribbon type morphology. The fibers had significant quantities of hydroxyl groups of Si—OH and Ti—OH. The fibers did not have crystalline structure. Diameters of the fibers were reduced by solvent evaporation and calcination. The hydroxyl groups on the fibers disappeared by calcination. The hydroxyl groups, M—OH (MSi, Ti) were changed to M—O—M by intermolecular and intramolecular condensation reactions. 相似文献
939.
LK Das SW Park SJ Cho A Ghosh 《Dalton transactions (Cambridge, England : 2003)》2012,41(36):11009-11017
Two new trinuclear hetero-metallic copper(ii)-zinc(ii) complexes [(CuL)(2)Zn(N(3))(2)] ( and ) have been synthesized using [CuL] as a so-called "metalloligand" (where H(2)L = N,N'-bis(salicylidene)-1,3-propanediamine) and structurally characterized. Complexes and have the same molecular formula but crystallize in different crystal systems (triclinic for and monoclinic for ) with space group P1[combining macron] for and P2(1)/c for . is an angular trinuclear species, in which two terminal four-coordinate square planar "metalloligand" [CuL] are coordinated to a central Zn(ii) through double phenoxido bridges. The Zn(ii) is in a six-coordinate distorted octahedral environment being bonded additionally to two mutually cis nitrogen atoms of terminal azide ions. In complex , in addition to the double phenoxido bridge, the two terminal Cu(ii) ions are linked to the central Zn(ii) via a μ(-l,l) azido bridge giving rise to a square pyramidal environment around the Cu(ii) ions and consequently the structure becomes linear. These two species can be considered as "linear-bent" isomers. EPR spectra and ESI mass spectra show that the two isomers are identical in solution. The DFT calculation reveals that the energy of is 7.06 kcal mol(-1) higher than that of . The existence of both isomers in the solid state suggests that crystal packing interactions in are more efficient and probably compensate for the difference in energy. 相似文献
940.
We present a method for generating fractal surfaces of dimension between two and three. By using the method, five fractal surfaces with dimension 2.262, 2.402, 2.524, 2.631, and 2.771 are created. For each of these surfaces, the reaction of carbon monoxide and oxygen is simulated by using a Monte Carlo method based on the ZGB model [Phys. Rev. Lett. 24 (1986) 2553]. The results show that the catalytic CO oxidation proceeds more efficiently on a surface with higher fractal dimension. It is also found that as the fractal dimension of the surface becomes higher, the first-order kinetic phase transition point (y2) is shifted to a higher partial pressure of CO. This implies that poisoning of the catalyst surface due to CO segregation sets in at a higher CO partial pressure for surfaces with more complexity. 相似文献